Methods and systems for corneal topography, blink detection and laser eye surgery

ABSTRACT

A method of blink detection in a laser eye surgical system includes providing a topography measurement structure having a geometric marker. The method includes bringing the topography measurement structure into a position proximal to an eye such that light traveling from the geometric marker is capable of reflecting off a refractive structure of the eye of the patient, and also detecting the light reflected from the structure of the eye for a predetermined time period while the topography measurement structure is at the proximal position. The method further includes converting the light reflected from the surface of the eye into image data and analyzing the image data to determine whether light reflected from the geometric marker is present is in the reflected light, wherein if the geometric marker is determined not to be present, the patient is identified as having blinked during the predetermined time.

RELATED APPLICATIONS

This application is a continuation application under 35 U.S.C. § 120 ofU.S. patent application Ser. No. 15/662,203, filed on 27 Jul. 2017, nowallowed, which in turn is a continuation application under 35 U.S.C. §120 of U.S. patent application Ser. No. 14/866,418, filed on 25 Sep.2015 and issued as U.S. Pat. No. 9,721,351, which is a non-provisionalapplication and claims the benefit under 35 U.S.C. § 119(e) of U.S.Provisional Application Ser. No. 62/055,429, filed Sep. 25, 2014. Thedisclosures of all of the above applications are incorporated herein intheir entireties as if fully set forth.

TECHNICAL FIELD

This disclosure relates generally to eye surgery, and more particularly,to methods and systems for corneal topography and blink detection inlaser eye surgery.

BACKGROUND

Several people have vision impairments associated with refractiveproperties of the eye, such as myopia (near-sightedness), hyperopia(far-sightedness) and astigmatism. Myopia occurs when light focusesbefore the retina, and hyperopia occurs when light is refracted to afocus behind the retina. Astigmatism occurs when the corneal curvatureis unequal in two or more directions. These vision impairments can becorrected with spectacles or contact lenses. Alternatively, the corneaof the eye can be reshaped surgically to provide the needed opticalcorrection.

Eye surgery has now become commonplace with some patients pursuing it asan elective procedure to avoid using contact lenses or glasses tocorrect refractive problems, and others pursuing it to correct adverseconditions such as cataracts. And, with recent developments in lasertechnology, laser surgery is becoming the technique of choice forophthalmic procedures. The reason eye surgeons prefer a surgical laserbeam over manual tools like microkeratomes and forceps is that the laserbeam can be focused precisely on extremely small amounts of oculartissue, thereby enhancing accuracy and reliability of the procedure.These in turn enable better wound healing and recovery followingsurgery.

Examples of surgically cutting eye tissues include cutting the corneaand/or the crystalline lens of the eye. The lens of the eye can be cutto remove a defect, such as a cataract. Other eye tissues, e.g. thecornea or the lens capsule may be cut to access the cataractous lens soit can be removed.

The cornea can also be cut and reshaped to correct a refractive error ofthe eye, for example with laser assisted in situ keratomileusis(“LASIK”), photorefractive keratectomy (“PRK”), radial keratotomy(“RK”), cornealplasty, astigmatic keratotomy, corneal relaxing incision(“CRT”), Limbal Relaxing Incision (“LRI”), and refractive lenticularextractions, such as small incision lenticular extractions, and flaplessrefractive lenticular extractions. With astigmatic keratotomy, cornealrelaxing incisions, and limbal relaxing incisions, the corneal cuts aremade in a well-defined manner and depth to allow the cornea to changeshape and become more spherical.

Different laser eye surgical systems use different types of laser beamsfor the various procedures and indications. These include, for instance,ultraviolet lasers, infrared lasers, and near-infrared, ultra-shortpulsed lasers. Ultra-short pulsed lasers emit radiation with pulsedurations as short as 10 femtoseconds and as long as 3 nanoseconds, anda wavelength between 300 nm and 3000 nm. Examples of laser systems thatprovide ultra-short pulsed laser beams include Abbott Medical Optics'iFS Advanced Femtosecond Laser, Abbott Medical Optics' IntraLase FSLaser, and OptiMedica's Catalys Precision Laser System.

In the commonly-known LASIK procedure, an ultra-short pulsed laser isused to cut a corneal flap to expose the corneal stroma forphotoablation with ultraviolet beams from an excimer laser.Photoablation of the corneal stroma with the excimer laser reshapes thecornea and corrects the refractive condition such as myopia, hyperopia,astigmatism, and the like.

Cataract extraction is also a frequently performed surgical procedurewith an estimated 15 million cataract surgeries performed per yearworldwide. Opacification of the natural crystalline lens of the lensleads to cataract formation. The cataract scatters light passing throughthe lens, thereby perceptibly degrading vision. A cataract can vary indegree from slight to complete opacity. Early in the development of anage-related cataract, the power of the lens may increase, causingnear-sightedness (myopia). Gradual yellowing and opacification of thelens may reduce the perception of blue colors as those shorterwavelengths are more strongly absorbed and scattered within thecataractous crystalline lens. Often, cataract formation progressesslowly, resulting in progressive vision loss.

Typically, cataract treatment involves replacing the opaque crystallinelens with an artificial intraocular lens (IOL). Cataract surgery can beperformed using a technique called phacoemulsification, in which anultrasonic tip with associated irrigation and aspiration ports is usedto sculpt the relatively hard nucleus of the lens to facilitate itsremoval through an opening made in the anterior lens capsule. The outermembrane of the lens, referred to as the lens capsule, contains thenucleus of the lens, which is often the site of the highest grade of thecataract.

Performing an anterior capsulotomy or capsulorhexis in which a smallround hole is formed in the anterior side of the lens capsule providesaccess to the lens nucleus. When a laser is used to cut the lenscapsule, the procedure is called capsulotomy, whereas when forceps andother manual surgical tools are used to tear the lens capsule, theprocedure is called a manual continuous curvilinear capsulorhexis (CCC).After the capsulotomy, the laser may be used to segment the cataractouslens to ease its removal from the eye. After removal of the lensnucleus, a synthetic foldable intraocular lens (IOL) can be insertedinto the remaining lens capsule of the eye.

Conventional ultra-short pulse laser systems have been used to cut eyetissue, and to treat many patients with cataracts. Sometimes, however,these systems may provide less than ideal results for treatment of atleast some patients' eyes. This may occur because the eye comprisescomplex optical structures, making the success of laser eye surgerydependent on the accurate and precise measurement of both the positionof the eye in connection with laser eye surgery system, as well as themeasurement and/or imaging of the eye structures themselves. Forexample, in some instances, misalignment of the eye with the surgicaltreatment apparatus may result in less than ideal placement ofincisions.

Other factors that may limit the usefulness of data provided to asurgical laser system from eye measurement devices, such as tomographyand topography systems. For example, there can be at least somedistortion of at least some of the images taken among different devices,and this distortion can make the placement of laser incisions less thanideal in at least some instances. Also, the use of different systems formeasurement and treatment can introduce alignment errors, may take moretime than would be ideal, and may increase the overall cost of surgeryso that fewer patients receive beneficial treatments.

Another factor that may affect the accuracy of positioning and eyestructure measurement is the occurrence of blinking. Blinking is thesemi-autonomic rapid closing and opening of the eyelid. A patient mayreflexively blink to protect the eye from perceived potential damage, ormay do spontaneously, generally at rate of 10 to 15 times a minute. Eachblink lasts for 100-400 milliseconds, during which it obstructs allpattern vision and attenuates light levels 100-folds. In addition, thereflection, refraction, and/or scattering of light from the eye lid isvastly different from the reflection, refraction, and/or scattering oflight off surfaces of the eye, such as the cornea. As a result, data oneye measurement and eye position based on the reflective, refractive orother properties of the eye may be less than ideal if that data wasobtained during a blink.

Traditionally, the laser surgical device operator ensures that thepatient is not blinking. But, the operator may miss one or more blinkswhile performing other tasks during eye surgery. Hence, there is a needfor a blink detection system and methods that account for a patient'sblinking during eye positioning and measurement.

BRIEF SUMMARY

Hence, to obviate one or more problems due to limitations anddisadvantages of the related art, one object of this disclose providesembodiments for improved imaging and positioning of a patient's eye bydetecting blinking during eye positioning and measurement.

A method of blink detection in a laser eye surgical system comprisesproviding a topography measurement structure having at least onegeometric marker, and placing the topography measurement structure intoa position proximal to an eye of a patient such that light travelingfrom the at least one geometric marker is capable of reflecting off arefractive structure of the eye of the patient. The refractive structureis the preferably the cornea and more preferably the tear film of thecornea.

The method includes detecting the light reflected from the eye of thepatient for a predetermined time period while the topography measurementstructure is at the proximal position, and converting the lightreflected from the surface of the eye in the predetermined time periodinto image data. The method includes analyzing the image data todetermine whether light from the geometric marker is detected in thereflected light, wherein if the geometric marker is determined not to bepresent, the patient is determined to have blinked during thepredetermined time. If the geometric marker is determined to be presentin the detected light, the patient is determined not to have blinkedduring the predetermined time.

The geometric marker is preferably one or more regular curves, such asone or more circles, lines, or ellipses. Preferably, the at least onegeometric marker comprises a circle. Alternatively, there may be aplurality of geometric markers, and the geometric markers comprise atleast two concentric circles.

In many embodiments, the step of analyzing the image data comprisesperforming at least one of a Hough transform of the image data, fittingthe image data and measuring a goodness of fit, and image correlationwith geometric marker template. In a preferred embodiment, the geometricmarker is one or more circles, and data is analyzed with the HoughTransform to identify whether the one or more circles is present in theimage data.

In many embodiments, the detecting step further comprises periodicallyre-detecting the light reflected from the surface of the eye, convertingthe reflected light to image data, and analyzing the image data at eachoccurrence of the periodic detection. In a preferred embodiment, theperiodic detection corresponds to a rate of 30 Hz.

In many embodiments, to provide improved imaging and ranging, methodsand systems of blink detection are used concurrently with anotherimaging or positioning measurement system. A method of improved imagingand ranging in a laser eye surgical system comprises providing atopography measurement structure having at least one geometric marker ata position proximal to an eye of a patient such that light travelingfrom the at least one geometric marker is capable of reflecting off arefractive surface of the eye of the patient. The refractive structureis preferably the cornea and more preferably, the tear film of thecornea.

The method includes generating structural or position data regarding apatient's eye, and during at least a portion of the generating step, andwhile the topography measurement structure is at the proximal position,periodically detecting the light reflected from the refractive structureof the patient's eye for a predetermined period of time. The method alsoincludes converting the light reflected from the surface of the eye forat least one predetermined time period into image data, and analyzingthe image data to determine whether light corresponding to the geometricmarker was present in the reflected light, wherein if the geometricmarker is determined not to be present, the patient is identified ashaving blinked in the predetermined time during the generating step. Ifthe geometric marker is determined to be present in the detected light,the patient is determined not to have blinked in the predetermined timeduring the generating step.

In some embodiments, the method includes re-generating the structural orposition data if it is determined that a blink occurred during thepredetermined time period.

In some embodiments, the method includes identifying that the structuralor position data corresponding to the time periods during which thepatient has been determined to have blinked are not accurate. In someembodiment, the method includes removing structural or position datacorresponding to the time periods during which the patient has beendetermined to have blinked.

The geometric marker is preferably one or more regular curves, such ascircles, lines, or ellipses. Preferably, the at least one geometricmarker comprises a circle. Alternatively, there may be a plurality ofgeometric markers, and the geometric markers comprise at least twoconcentric circles.

In many embodiments, the step of analyzing the image data comprisesperforming at least one of a Hough transform of the image data, fittingthe image data and measuring a goodness of fit, and image correlationwith geometric marker template. In a preferred embodiment, the geometricmarker is one or more circles and data is analyzed with the HoughTransform to identify whether the one or more circles is present in theimage data.

In many embodiments, an apparatus for detecting the blink of an eye in apatient comprises a topography measurement system having at least onegeometric marker, the topography measurement system for measuring atopography of the cornea of the eye; an image capture device configuredto capture an image of the light reflected from a refractive structureof the eye of the patient for a predetermined period of time; and aprocessor comprising a tangible medium configured to analyze thecaptured image to determine whether light corresponding to the geometricmarker is present in the captured image, wherein if light correspondingto the geometric marker is not present in the captured image, theprocessor reports that the eye blinked during the predetermined timeperiod.

In many embodiments, the blink detection methods are used concurrentlywith the generation of a surface profile of the cornea to determinewhether the patient has blinked during the measurement of the surface.The surface profile of the cornea is measured when the eye is placed inan undistorted shape, for example, without being in contact with anexternal structure such as a patient interface, such that distortion ofthe cornea and measurement distortion is substantially inhibited. Whenthe eye has been placed in an undistorted configuration, such as whenthe patient is supported with a patient support of the laser surgerysystem and views the fixation light, the cornea of the eye can beexposed to air with a tear film, or other liquid over the cornea. Thesurface profile of the substantially undistorted cornea can be measuredin one or more of many ways, and may comprise one or more of an anteriorcorneal surface topography profile, a posterior a corneal surfacetopography profile, or a corneal thickness profile. In many embodiments,the surface profile comprises a representation of a three-dimensionalprofile, and may comprise an extraction of one or more parameters fromone or more images, such as an extraction of keratometry values from acorneal topography system or a tomography system integrated with thesurgical laser. The one or more parameters can be used to determine atissue treatment pattern on the eye, such as the angular location,depth, arc length, and anterior to posterior dimensions of relaxingincisions. Alternatively, or in combination, a first image of the eyecan be generated for aligning the eye, such as a pupil image of the eyewhen the eye rests naturally and the surface profile is measured.

This summary and the following detailed description are merelyexemplary, illustrative, and explanatory, and are not intended to limit,but to provide further explanation of the invention as claimed.Additional features and advantages of the invention will be set forth inthe descriptions that follow, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription, claims and the appended drawings.

BRIEF DESCRIPTION OF THE FIGURES

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages will be facilitated by referring to the following detaileddescription that sets forth illustrative embodiments using principles ofthe invention, as well as to the accompanying drawings, in which likenumerals refer to like parts throughout the different views. Like parts,however, do not always have like reference numerals. Further, thedrawings are not drawn to scale, and emphasis has instead been placed onillustrating the principles of the invention. All illustrations areintended to convey concepts, where relative sizes, shapes, and otherdetailed attributes may be illustrated schematically rather thandepicted literally or precisely.

FIG. 1 shows a perspective view showing a laser eye surgery systemaccording to many embodiments;

FIG. 2 shows a simplified block diagram showing a top level view of theconfiguration of a laser eye surgery system according to manyembodiments;

FIG. 3A shows a simplified block diagram illustrating the configurationof an optical assembly of a laser eye surgery system according to manyembodiments;

FIG. 3B shows a mapped treatment region of the eye comprising thecornea, the posterior capsule, and the limbus according to manyembodiments;

FIG. 4A shows correspondence among movable and sensor components of thelaser delivery system according to many embodiments;

FIG. 4B shows mapping of coordinate references from an eye spacecoordinate reference system to a machine coordinate reference systemaccording to many embodiments;

FIG. 5A shows a topography measurement structure configured to couple toa patient interface to measure the eye prior to the eye contacting thepatient interface according to embodiments;

FIG. 5B shows components of the patient interface and the topographymeasurement structure configured to couple to the patient interfaceaccording to many embodiments;

FIG. 5C shows discrete points of reflected light from the cornea basedon the geometric marker of topography measurement structure;

FIG. 5D shows components of the patient interface and the topographymeasurement structure configured to couple to the patient interface.

FIG. 5E shows a perspective view of the interface end of the topographymeasurement structure;

FIG. 5F shows a perspective view of the working end of the topographymeasurement structure;

FIG. 6 shows a flow chart for performing a method of blink detection 600in a laser eye surgical system.

FIGS. 7A shows displayed image data of a geometric marker in the casewhere the geometric marker is two concentric circles.

FIG. 7B shows the result of the circular Hough Transform in parameterspace (a,b).

FIGS. 8A and 8B illustrate the operation of a blink detection andcorneal topography system according to many embodiments of theinvention. FIG. 8A illustrates the operation of the corneal topographyand blink detection system when the eye is open. FIG. 8B illustrates theoperation of the corneal topography and blink detection system when theeye is closed.

FIG. 9 shows a flow chart of a method for providing accurate anddistortion-free corneal topography measurement and subsequentintegration with the laser treatment, according to embodiments.

DETAILED DESCRIPTION OF THE INVENTION

Methods and systems related to laser eye surgery are disclosed. In manyembodiments, a laser is used to form precise incisions in the cornea, inthe lens capsule, and/or in the crystalline lens nucleus. Althoughspecific reference is made to tissue incisions for laser eye surgery,the embodiments in this disclosure can be used in one or more of manyways with many surgical procedures such as orthopedic surgery androbotic surgery, as well as with many surgical devices, includingmicrokeratomes.

The embodiments described here are particularly well-suited for treatingtissue, such as surgically treating tissue. In many embodiments, thetissue comprises an optically transmissive tissue, such as tissue of aneye. The embodiments described here can be combined in many ways withone or more of many known refractive and cataract surgical procedures,including for example, one or more procedures for laser cataractsurgery, corneal incisions, LASIK, all laser LASIK, femto LASIK,corneaplasty, astigmatic keratotomy, corneal relaxing incisions, limbalrelaxing incisions, PRK, RK, refractive lenticular extractions, andsmall incision lenticule extractions.

Methods and systems of blink detection are disclosed. These method andsystems may be advantageously used in connection with othermeasurements, such as the determination of the position or measurementof eye structures, to determine whether a blink has occurred during themeasurement.

The embodiments disclosed here are also well-suited for combination withcorneal measurement systems. The corneal measurement system may comprisea component of the laser surgery system, which allows the cornea to bemeasured with the corneal measurement system when the patient issupported with a patient support such as a surgical bed coupled to thelaser surgery system. Alternatively, the corneal measurement system maycomprise a corneal measurement system separated from the laser system,such as that located in another room of a physician's office.

The embodiments disclosed here are well-suited for combination withlaser surgery systems, such OptiMedica's Catalys Precision Laser System,AMO's iFS Laser System, and similar systems. Such systems can bemodified according to the teachings disclosed so as to more accuratelymeasure and treat the eye.

As used here, the terms anterior and posterior refer to knownorientations with respect to the patient. Depending on the orientationof the patient during surgery, the terms anterior and posterior may besimilar to the terms upper and lower, respectively, such as when thepatient is placed in a supine position on a bed. The terms distal andanterior may refer to an orientation of a structure from the perspectiveof the user, such that the terms proximal and distal may be similar tothe terms anterior and posterior when referring to a structure placed onthe eye, for example. A person of ordinary skill in the art willrecognize many variations of the orientation of the methods andapparatus as described here, and the terms anterior, posterior,proximal, distal, upper, and lower are used merely by way of example.

As used here, the terms first and second are used to describe structuresand methods without limitation as to the order of the structures and themethods, which can be in any order, as will be apparent to a person ofordinary skill in the art based on the teachings provided here.

As used here, the term anterior and posterior nodal points of the eyemay have the property that a ray aimed at one node will be refracted bythe eye such that it appears to have come from the other node, and withthe same angle with respect to the optical axis.

FIG. 1 shows a laser eye surgery system 2, according to manyembodiments, operable to form precise incisions in the cornea, in thelens capsule, and/or in the crystalline lens nucleus. The system 2includes a main unit 4, a patient chair 6, a dual function footswitch 8,and a laser footswitch 10.

The main unit 4 includes many primary subsystems of the system 2. Forexample, externally visible subsystems include a touch-screen displaycontrol panel 12, a patient interface assembly 14, patient interfacevacuum connections 16, a docking control keypad 18, a patient interfaceradio frequency identification (RFID) reader 20, external connections 22(e.g., network, video output, footswitch, USB port, door interlock, andAC power), laser emission indicator 24, emergency laser stop button 26,key switch 28, and USB data ports 30.

The patient chair 6 includes a base 32, a patient support bed 34, aheadrest 36, a positioning mechanism, and a patient chair joystickcontrol 38 disposed on the headrest 36. The positioning controlmechanism is coupled between the base 32 and the patient support bed 34and headrest 36. The patient chair 6 is configured to be adjusted andoriented in three axes (x, y, and z) using the patient chair joystickcontrol 38. The headrest 36 and a restrain system (not shown, e.g., arestraint strap engaging the patient's forehead) stabilize the patient'shead during the procedure. The headrest 36 includes an adjustable necksupport to provide patient comfort and to reduce patient head movement.The headrest 36 is configured to be vertically adjustable to enableadjustment of the patient head position to provide patient comfort andto accommodate variation in patient head size.

The patient chair 6 allows for tilt articulation of the patient's legs,torso, and head using manual adjustments. The patient chair 6accommodates a patient load position, a suction ring capture position,and a patient treat position. In the patient load position, the chair 6is rotated out from under the main unit 4 with the patient chair back inan upright position and patient footrest in a lowered position. In thesuction ring capture position, the chair is rotated out from under themain unit 4 with the patient chair back in reclined position and patientfootrest in raised position. In the patient treat position, the chair isrotated under the main unit 4 with the patient chair back in reclinedposition and patient footrest in raised position.

The patient chair 6 is equipped with a “chair enable” feature to protectagainst unintended chair motion. The patient chair joystick 38 can beenabled in either of two ways. First, the patient chair joystick 38incorporates a “chair enable” button located on the top of the joystick.Control of the position of the patient chair 6 via the joystick 38 canbe enabled by continuously pressing the “chair enable” button.Alternately, the left foot switch 40 of the dual function footswitch 8can be continuously depressed to enable positional control of thepatient chair 6 via the joystick 38.

In many embodiments, the patient control joystick 38 is a proportionalcontroller. For example, moving the joystick a small amount can be usedto cause the chair to move slowly. Moving the joystick a large amountcan be used to cause the chair to move faster. Holding the joystick atits maximum travel limit can be used to cause the chair to move at themaximum chair speed. The available chair speed can be reduced as thepatient approaches the patient interface assembly 14.

The emergency stop button 26 can be pushed to stop emission of all laseroutput, release vacuum that couples the patient to the system 2, anddisable the patient chair 6. The stop button 26 is located on the systemfront panel, next to the key switch 28.

The key switch 28 can be used to enable the system 2. When in a standbyposition, the key can be removed and the system is disabled. When in aready position, the key enables power to the system 2.

The dual function footswitch 8 is a dual footswitch assembly thatincludes the left foot switch 40 and a right foot switch 42. The leftfoot switch 40 is the “chair enable” footswitch. The right footswitch 42is a “vacuum ON” footswitch that enables vacuum to secure a liquidoptics interface suction ring to the patient's eye. The laser footswitch10 is a shrouded footswitch that activates the treatment laser whendepressed while the system is enabled.

In many embodiments, the system 2 includes external communicationconnections. For example, the system 2 can include a network connection(e.g., an RJ45 network connection) for connecting the system 2 to anetwork. The network connection can be used to enable network printingof treatment reports, remote access to view system performance logs, andremote access to perform system diagnostics. The system 2 can include avideo output port (e.g., HDMI) that can be used to output video oftreatments performed by the system 2. The output video can be displayedon an external monitor for, for example, viewing by family membersand/or training. The output video can also be recorded for, for example,archival purposes. The system 2 can include one or more data outputports (e.g., USB) to enable export of treatment reports to a datastorage device. The treatments reports stored on the data storage devicecan then be accessed at a later time for any suitable purpose such as,for example, printing from an external computer in the case where theuser without access to network based printing.

FIG. 2 shows a simplified block diagram of the system 2 coupled with apatient eye 43. The patient eye 43 comprises a cornea 43C, a lens 43Land an iris 431. The iris 431 defines a pupil of the eye 43 that may beused for alignment of eye 43 with system 2. The system 2 includes acutting laser subsystem 44, a ranging subsystem 46, an alignmentguidance system 48, shared optics 50, a patient interface 52, controlelectronics 54, a control panel/GUI 56, user interface devices 58, andcommunication paths 60. The control electronics 54 is operativelycoupled via the communication paths 60 with the cutting laser subsystem44, the ranging subsystem 46, the alignment guidance subsystem 48, theshared optics 50, the patient interface 52, the control panel/GUI 56,and the user interface devices 58.

The laser eye surgery system 2A comprises an imaging subsystem 51 whichmay be used to visualize and image the eye 43, and the control panel/GUI56 comprises a display 59. The laser eye surgery system 2 may beconfigured to couple to a corneal diagnostic system 53. For the lasereye surgery system 2, the OCT system of the ranging subsystem 46 may beused to position the patient eye and/or to measure the shape of thecornea as discussed herein. For the laser eye surgery system 2, cornealtopography system 53 may be used to measure the shape of the cornea. Thecorneal topography system 53 may apply any number of modalities tomeasure the shape of the eye including one or more of a keratometryreading of the eye, a corneal topography of the eye, an opticalcoherence tomography of the eye, a Placido disc topography of the eye, areflection of a plurality of points from the cornea topography of theeye, a grid reflected from the cornea of the eye topography, aHartmann-Shack measurement of the eye, a Scheimpflug image topography ofthe eye, a confocal tomography of the eye, or a low coherencereflectometry of the eye. The shape of the cornea can be measuredbefore, during, or after the patient interface 52 is docked with the eyeof the patient. Images captured by the ranging subsystem 46 of the lasereye surgery system 2 or the imaging subsystem 51 of the laser eyesurgery system 2 and the corneal topography system 53 may be displayedwith a display of the control panel/GUI 56 of the laser eye surgerysystem 2 or the display 59 of the laser eye surgery system 2,respectively. The control panel/GUI 56 may also be used to modify,distort, or transform any of the displayed images.

In many embodiments, the cutting laser subsystem 44 incorporatesfemtosecond (FS) laser technology. By using femtosecond lasertechnology, a short duration (e.g., approximately 10⁻¹³ seconds induration) laser pulse (with energy level in the micro joule range) canbe delivered to a tightly focused point to disrupt tissue, therebysubstantially lowering the energy level required as compared to thelevel required for ultrasound fragmentation of the lens nucleus and ascompared to laser pulses having longer durations.

The cutting laser subsystem 44 can produce laser pulses having awavelength suitable to the configuration of the system 2. As anon-limiting example, the system 2 can be configured to use a cuttinglaser subsystem 44 that produces laser pulses having a wavelength from1020 nm to 1050 nm. For example, the cutting laser subsystem 44 can havea diode-pumped solid-state configuration with a 1030 (+/−5) nm centerwavelength.

The cutting laser subsystem 44 can include control and conditioningcomponents. For example, such control components can include componentssuch as a beam attenuator to control the energy of the laser pulse andthe average power of the pulse train, a fixed aperture to control thecross-sectional spatial extent of the beam containing the laser pulses,one or more power monitors to monitor the flux and repetition rate ofthe beam train and therefore the energy of the laser pulses, and ashutter to allow/block transmission of the laser pulses. Suchconditioning components can include an adjustable zoom assembly to adaptthe beam containing the laser pulses to the characteristics of thesystem 2 and a fixed optical relay to transfer the laser pulses over adistance while accommodating laser pulse beam positional and/ordirectional variability, thereby providing increased tolerance forcomponent variation.

The ranging subsystem 46 is configured to measure the spatialdisposition of eye structures in three dimensions. The measured eyestructures can include the anterior and posterior surfaces of thecornea, the anterior and posterior portions of the lens capsule, theiris, and the limbus. In many embodiments, the ranging subsystem 46utilizes optical coherence tomography (OCT) imaging. As a non-limitingexample, the system 2 can be configured to use an OCT imaging systememploying wavelengths from 780 nm to 970 nm. For example, the rangingsubsystem 46 can include an OCT imaging system that employs a broadspectrum of wavelengths from 810 nm to 850 nm. Such an OCT imagingsystem can employ a reference path length that is adjustable to adjustthe effective depth in the eye of the OCT measurement, thereby allowingthe measurement of system components including features of the patientinterface that lie anterior to the cornea of the eye and structures ofthe eye that range in depth from the anterior surface of the cornea tothe posterior portion of the lens capsule and beyond.

The alignment guidance subsystem 48 can include a laser diode or gaslaser that produces a laser beam used to align optical components of thesystem 2. The alignment guidance subsystem 48 can include LEDs or lasersthat produce a fixation light to assist in aligning and stabilizing thepatient's eye during docking and treatment. The alignment guidancesubsystem 48 can include a laser or LED light source and a detector (notshown) to monitor the alignment and stability of the actuators used toposition the beam in X, Y, and Z. The alignment guidance subsystem 48can include a video system that can be used to provide imaging of thepatient's eye to facilitate docking of the patient's eye 43 to thepatient interface 52. The imaging system provided by the video systemcan also be used to direct via the GUI the location of cuts. The imagingprovided by the video system can additionally be used during the lasereye surgery procedure to monitor the progress of the procedure, to trackmovements of the patient's eye 43 during the procedure, and to measurethe location and size of structures of the eye such as the pupil and/orlimbus.

The shared optics 50 provides a common propagation path that is disposedbetween the patient interface 52 and each of the cutting laser subsystem44, the ranging subsystem 46, and the alignment guidance subsystem 48.In many embodiments, the shared optics 50 includes beam combiners toreceive the emission from the respective subsystem (e.g., the cuttinglaser subsystem 44, and the alignment guidance subsystem 48) andredirect the emission along the common propagation path to the patientinterface. In many embodiments, the shared optics 50 includes anobjective lens assembly that focuses each laser pulse into a focalpoint. In many embodiments, the shared optics 50 includes scanningmechanisms operable to scan the respective emission in three dimensions.For example, the shared optics can include an XY-scan mechanism(s) and aZ-scan mechanism. The XY-scan mechanism(s) can be used to scan therespective emission in two dimensions transverse to the propagationdirection of the respective emission. The Z-scan mechanism can be usedto vary the depth of the focal point within the eye 43. In manyembodiments, the scanning mechanisms are disposed between the laserdiode and the objective lens such that the scanning mechanisms are usedto scan the alignment laser beam produced by the laser diode. Incontrast, in many embodiments, the video system is disposed between thescanning mechanisms and the objective lens such that the scanningmechanisms do not affect the image obtained by the video system.

The patient interface 52 is used to restrain the position of thepatient's eye 43 relative to the system 2. In many embodiments, thepatient interface 52 employs a suction ring that is vacuum attached tothe patient's eye 43. The suction ring is then coupled with the patientinterface 52, for example, using vacuum to secure the suction ring tothe patient interface 52. In many embodiments, the patient interface 52includes an optically transmissive structure having a posterior surfacethat is displaced vertically from the anterior surface of the patient'scornea and a region of a suitable liquid (e.g., a sterile bufferedsaline solution (BSS) such as Alcon BSS (Alcon Part Number 351-55005-1)or equivalent) is disposed between and in contact with the patientinterface lens posterior surface and the patient's cornea and forms partof a transmission path between the shared optics 50 and the patient'seye 43. The optically transmissive structure may comprise a lens 96having one or more curved surfaces. Alternatively, the patient interface52 may comprise an optically transmissive structure having one or moresubstantially flat surfaces such as a parallel plate or wedge. In manyembodiments, the patient interface lens is disposable and can bereplaced at any suitable interval, such as before each eye treatment.

The control electronics 54 controls the operation of and can receiveinput from the cutting laser subsystem 44, the ranging subsystem 46, thealignment guidance subsystem 48, the patient interface 52, the controlpanel/GUI 56, and the user interface devices 58 via the communicationpaths 60. The communication paths 60 can be implemented in any suitableconfiguration, including any suitable shared or dedicated communicationpaths between the control electronics 54 and the respective systemcomponents. The control electronics 54 can include any suitablecomponents, such as one or more processor, one or morefield-programmable gate array (FPGA), and one or more memory storagedevices. In many embodiments, the control electronics 54 controls thecontrol panel/GUI 56 to provide for pre-procedure planning according touser specified treatment parameters as well as to provide user controlover the laser eye surgery procedure.

The user interface devices 58 can include any suitable user input devicesuitable to provide user input to the control electronics 54. Forexample, the user interface devices 58 can include devices such as, forexample, the dual function footswitch 8, the laser footswitch 10, thedocking control keypad 18, the patient interface radio frequencyidentification (RFID) reader 20, the emergency laser stop button 26, thekey switch 28, and the patient chair joystick control 38.

FIG. 3A is a simplified block diagram illustrating an assembly 62,according to many embodiments, that can be included in the system 2. Theassembly 62 is a non-limiting example of suitable configurations andintegration of the cutting laser subsystem 44, the ranging subsystem 46,the alignment guidance subsystem 48, the shared optics 50, and thepatient interface 52. Other configurations and integration of thecutting laser subsystem 44, the ranging subsystem 46, the alignmentguidance subsystem 48, the shared optics 50, and the patient interface52 may be possible and may be apparent to a person of skill in the art.

The assembly 62 is operable to project and scan optical beams into thepatient's eye 43. The cutting laser subsystem 44 includes an ultrafast(UF) laser 64 (e.g., a femtosecond laser). Using the assembly 62,optical beams can be scanned in the patient's eye 43 in threedimensions: X, Y, Z. For example, short-pulsed laser light generated bythe UF laser 64 can be focused into eye tissue to produce dielectricbreakdown to cause photodisruption around the focal point (the focalzone), thereby rupturing the tissue in the vicinity of the photo-inducedplasma. In the assembly 62, the wavelength of the laser light can varybetween 800 nm to 1200 nm and the pulse width of the laser light canvary from 10 fs to 10000 fs. The pulse repetition frequency can alsovary from 10 kHz to 500 kHz. Safety limits with regard to unintendeddamage to non-targeted tissue bound the upper limit with regard torepetition rate and pulse energy. Threshold energy, time to complete theprocedure, and stability can bound the lower limit for pulse energy andrepetition rate. The peak power of the focused spot in the eye 43 andspecifically within the crystalline lens and the lens capsule of the eyeis sufficient to produce optical breakdown and initiate aplasma-mediated ablation process. Near-infrared wavelengths for thelaser light are preferred because linear optical absorption andscattering in biological tissue is reduced for near-infraredwavelengths. As an example, the laser 64 can be a repetitively pulsed1031 nm device that produces pulses with less than 600 fs duration at arepetition rate of 120 kHz (+/−5%) and individual pulse energy in the 1to 20 micro joule range.

The cutting laser subsystem 44 is controlled by the control electronics54 and the user, via the control panel/GUI 56 and the user interfacedevices 58, to create a laser pulse beam 66. The control panel/GUI 56 isused to set system operating parameters, process user input, displaygathered information such as images of ocular structures, and displayrepresentations of incisions to be formed in the patient's eye 43.

The generated laser pulse beam 66 proceeds through a zoom assembly 68.The laser pulse beam 66 may vary from unit to unit, particularly whenthe UF laser 64 may be obtained from different laser manufacturers. Forexample, the beam diameter of the laser pulse beam 66 may vary from unitto unit (e.g., by +/−20%). The beam may also vary with regard to beamquality, beam divergence, beam spatial circularity, and astigmatism. Inmany embodiments, the zoom assembly 68 is adjustable such that the laserpulse beam 66 exiting the zoom assembly 68 has consistent beam diameterand divergence unit to unit.

After exiting the zoom assembly 68, the laser pulse beam 66 proceedsthrough an attenuator 70. The attenuator 70 is used to adjust thetransmission of the laser beam and thereby the energy level of the laserpulses in the laser pulse beam 66. The attenuator 70 is controlled viathe control electronics 54.

After exiting the attenuator 70, the laser pulse beam 66 proceedsthrough an aperture 72. The aperture 72 sets the outer useful diameterof the laser pulse beam 66. In turn the zoom determines the size of thebeam at the aperture location and therefore the amount of light that istransmitted. The amount of transmitted light is bounded both high andlow. The upper is bounded by the requirement to achieve the highestnumerical aperture achievable in the eye. High NA promotes low thresholdenergies and greater safety margin for untargeted tissue. The lower isbound by the requirement for high optical throughput. Too muchtransmission loss in the system shortens the lifetime of the system asthe laser output and system degrades over time. Additionally,consistency in the transmission through this aperture promotes stabilityin determining optimum settings (and sharing of) for each procedure.Typically, to achieve optimal performance, the transmission through thisaperture is set in the range between 88% to 92%.

After exiting the aperture 72, the laser pulse beam 66 proceeds throughtwo output pickoffs 74. Each output pickoff 74 can include a partiallyreflecting mirror to divert a portion of each laser pulse to arespective output monitor 76. Two output pickoffs 74 (e.g., a primaryand a secondary) and respective primary and secondary output monitors 76are used to provide redundancy in case of malfunction of the primaryoutput monitor 76.

After exiting the output pickoffs 74, the laser pulse beam 66 proceedsthrough a system-controlled shutter 78. The system-controlled shutter 78ensures on/off control of the laser pulse beam 66 for procedural andsafety reasons. The two output pickoffs precede the shutter allowing formonitoring of the beam power, energy, and repetition rate as apre-requisite for opening the shutter.

After exiting the system-controlled shutter 78, the optical beamproceeds through an optics relay telescope 80. The optics relaytelescope 80 propagates the laser pulse beam 66 over a distance whileaccommodating positional and/or directional variability of the laserpulse beam 66, thereby providing increased tolerance for componentvariation. As an example, the optical relay can be a Keplerian afocaltelescope that relays an image of the aperture position to a conjugateposition near to the xy galvo mirror positions. In this way, theposition of the beam at the XY galvo location is invariant to changes inthe beams angle at the aperture position. Similarly the shutter does nothave to precede the relay and may follow after or be included within therelay.

After exiting the optics relay telescope 80, the laser pulse beam 66 istransmitted to the shared optics 50, which propagates the laser pulsebeam 66 to the patient interface 52. The laser pulse beam 66 is incidentupon a beam combiner 82, which reflects the laser pulse beam 66 whiletransmitting optical beams from the ranging subsystem 46 and thealignment guidance subsystem: AIM 48.

Following the beam combiner 82, the laser pulse beam 66 continuesthrough a Z telescope 84, which is operable to scan focus position ofthe laser pulse beam 66 in the patient's eye 43 along the Z axis. Forexample, the Z-telescope 84 can include a Galilean telescope with twolens groups (each lens group includes one or more lenses). One of thelens groups moves along the Z axis about the collimation position of theZ-telescope 84. In this way, the focus position of the spot in thepatient's eye 43 moves along the Z axis. In general, there is arelationship between the motion of lens group and the motion of thefocus point. For example, the Z-telescope can have an approximate 2×beam expansion ratio and close to a 1:1 relationship of the movement ofthe lens group to the movement of the focus point. The exactrelationship between the motion of the lens and the motion of the focusin the z axis of the eye coordinate system does not have to be a fixedlinear relationship. The motion can be nonlinear and directed via amodel or a calibration from measurement or a combination of both.Alternatively, the other lens group can be moved along the Z axis toadjust the position of the focus point along the Z axis. The Z-telescope84 functions as z-scan device for scanning the focus point of thelaser-pulse beam 66 in the patient's eye 43. The Z-telescope 84 can becontrolled automatically and dynamically by the control electronics 54and selected to be independent or to interplay with the X and Y scandevices described next.

After passing through the Z-telescope 84, the laser pulse beam 66 isincident upon an X-scan device 86, which is operable to scan the laserpulse beam 66 in the X direction, which is dominantly transverse to theZ axis and transverse to the direction of propagation of the laser pulsebeam 66. The X-scan device 86 is controlled by the control electronics54, and can include suitable components, such as a motor, galvanometer,or any other well-known optic moving device. The relationship of themotion of the beam as a function of the motion of the X actuator doesnot have to be fixed or linear. Modeling or calibrated measurement ofthe relationship or a combination of both can be determined and used todirect the location of the beam.

After being directed by the X-scan device 86, the laser pulse beam 66 isincident upon a Y scan device 88, which is operable to scan the laserpulse beam 66 in the Y direction, which is dominantly transverse to theX and Z axes. The Y-scan device 88 is controlled by the controlelectronics 54, and can include suitable components, such as a motor,galvanometer, or any other well-known optic moving device. Therelationship of the motion of the beam as a function of the motion ofthe Y actuator does not have to be fixed or linear. Modeling orcalibrated measurement of the relationship or a combination of both canbe determined and used to direct the location of the beam.Alternatively, the functionality of the X-Scan device 86 and the Y-Scandevice 88 can be provided by an XY-scan device configured to scan thelaser pulse beam 66 in two dimensions transverse to the Z axis and thepropagation direction of the laser pulse beam 66. The X-scan and Y scandevices 86, 88 change the resulting direction of the laser pulse beam66, causing lateral displacements of UF focus point located in thepatient's eye 43.

After being directed by the Y-scan device 88, the laser pulse beam 66passes through a beam combiner 90. The beam combiner 90 is configured totransmit the laser pulse beam 66 while reflecting optical beams to andfrom a video subsystem 92 of the alignment guidance subsystem 48.

After passing through the beam combiner 90, the laser pulse beam 66passes through an objective lens assembly 94. The objective lensassembly 94 can include one or more lenses. In many embodiments, theobjective lens assembly 94 includes multiple lenses. The complexity ofthe objective lens assembly 94 may be driven by the scan field size, thefocused spot size, the degree of telecentricity, the available workingdistance on both the proximal and distal sides of objective lensassembly 94, as well as the amount of aberration control.

After passing through the objective lens assembly 94, the laser pulsebeam 66 passes through the patient interface 52. As described above, inmany embodiments, the patient interface 52 includes a patient interfacelens 96 having a posterior surface that is displaced vertically from theanterior surface of the patient's cornea and a region of a suitableliquid (e.g., a sterile buffered saline solution (BSS) such as Alcon BSS(Alcon Part Number 351-55005-1) or equivalent) is disposed between andin contact with the posterior surface of the patient interface lens 96and the patient's cornea and forms part of an optical transmission pathbetween the shared optics 50 and the patient's eye 43.

The shared optics 50 under the control of the control electronics 54 canautomatically generate aiming, ranging, and treatment scan patterns.Such patterns can be comprised of a single spot of light, multiple spotsof light, a continuous pattern of light, multiple continuous patterns oflight, and/or any combination of these. In addition, the aiming pattern(using the aim beam 108 described below) need not be identical to thetreatment pattern (using the laser pulse beam 66), but can optionally beused to designate the boundaries of the treatment pattern to provideverification that the laser pulse beam 66 will be delivered only withinthe desired target area for patient safety. This can be done, forexample, by having the aiming pattern provide an outline of the intendedtreatment pattern. This way the spatial extent of the treatment patterncan be made known to the user, if not the exact locations of theindividual spots themselves, and the scanning thus optimized for speed,efficiency, and/or accuracy. The aiming pattern can also be made to beperceived as blinking in order to further enhance its visibility to theuser. Likewise, the ranging beam 102 need not be identical to thetreatment beam or pattern. The ranging beam needs only to be sufficientenough to identify targeted surfaces. These surfaces can include thecornea and the anterior and posterior surfaces of the lens and may beconsidered spheres with a single radius of curvature. Also, the opticsshared by the alignment guidance: video subsystem does not have to beidentical to those shared by the treatment beam. The positioning andcharacter of the laser pulse beam 66 and/or the scan pattern the laserpulse beam 66 forms on the eye 43 may be further controlled by use of aninput device such as a joystick, or any other appropriate user inputdevice (e.g., control panel/GUI 56) to position the patient and/or theoptical system.

The control electronics 54 can be configured to target the targetedstructures in the eye 43 and ensure that the laser pulse beam 66 will befocused where appropriate and not unintentionally damage non-targetedtissue. Imaging modalities and techniques described herein, such asthose mentioned above, or ultrasound may be used to determine thelocation and measure the thickness of the lens and lens capsule toprovide greater precision to the laser focusing methods, including 2Dand 3D patterning. Laser focusing may also be accomplished by using oneor more methods including direct observation of an aiming beam, or otherknown ophthalmic or medical imaging modalities, such as those mentionedabove, and/or combinations thereof. Additionally, the ranging subsystemsuch as an OCT can be used to detect features or aspects involved withthe patient interface. Features can include fiducials placed on thedocking structures and optical structures of the disposable lens such asthe location of the anterior and posterior surfaces.

In the embodiment of FIG. 3A, the ranging subsystem 46 includes an OCTimaging device. Additionally or alternatively, imaging modalities otherthan OCT imaging can be used. An OCT scan of the eye can be used tomeasure the spatial disposition (e.g., three-dimensional coordinatessuch as X, Y, and Z of points on boundaries) of structures of interestin the patient's eye 43. Such structure of interest can include, forexample, the anterior surface of the cornea, the posterior surface ofthe cornea, the anterior portion of the lens capsule, the posteriorportion of the lens capsule, the anterior surface of the crystallinelens, the posterior surface of the crystalline lens, the iris, thepupil, and/or the limbus. The spatial disposition of the structures ofinterest and/or of suitable matching geometric modeling such as surfacesand curves can be generated and/or used by the control electronics 54 toprogram and control the subsequent laser-assisted surgical procedure.The spatial disposition of the structures of interest and/or of suitablematching geometric modeling can also be used to determine a wide varietyof parameters related to the procedure such as, for example, the upperand lower axial limits of the focal planes used for cutting the lenscapsule and segmentation of the lens cortex and nucleus, and thethickness of the lens capsule among others.

The ranging subsystem 46 in FIG. 3A includes an OCT light source anddetection device 98. The OCT light source and detection device 98includes a light source that generates and emits light with a suitablebroad spectrum. For example, in many embodiments, the OCT light sourceand detection device 98 generates and emits light with a broad spectrumfrom 810 nm to 850 nm wavelength. The generated and emitted light iscoupled to the device 98 by a single mode fiber optic connection.

The light emitted from the OCT light source and detection device 98 ispassed through a beam combiner 100, which divides the light into asample portion 102 and a reference portion 104. A significant portion ofthe sample portion 102 is transmitted through the shared optics 50. Arelative small portion of the sample portion is reflected from thepatient interface 52 and/or the patient's eye 43 and travels backthrough the shared optics 50, back through the beam combiner 100 andinto the OCT light source and detection device 98. The reference portion104 is transmitted along a reference path 106 having an adjustable pathlength. The reference path 106 is configured to receive the referenceportion 104 from the beam combiner 100, propagate the reference portion104 over an adjustable path length, and then return the referenceportion 106 back to the beam combiner 100, which then directs thereturned reference portion 104 back to the OCT light source anddetection device 98. The OCT light source and detection device 98 thendirects the returning small portion of the sample portion 102 and thereturning reference portion 104 into a detection assembly, which employsa time domain detection technique, a frequency detection technique, or asingle point detection technique. For example, a frequency-domaintechnique can be used with an OCT wavelength of 830 nm and bandwidth of10 nm.

Once combined with the UF laser pulse beam 66 subsequent to the beamcombiner 82, the OCT sample portion beam 102 follows a shared path withthe UF laser pulse beam 66 through the shared optics 50 and the patientinterface 52. In this way, the OCT sample portion beam 102 is generallyindicative of the location of the UF laser pulse beam 66. Similar to theUF laser beam, the OCT sample portion beam 102 passes through theZ-telescope 84, is redirected by the X-scan device 86 and by the Y-scandevice 88, passes through the objective lens assembly 94 and the patientinterface 52, and on into the eye 43. Reflections and scatter off ofstructures within the eye provide return beams that retrace back throughthe patient interface 52, back through the shared optics 50, backthrough the beam combiner 100, and back into the OCT light source anddetection device 98. The returning back reflections of the sampleportion 102 are combined with the returning reference portion 104 anddirected into the detector portion of the OCT light source and detectiondevice 98, which generates OCT signals in response to the combinedreturning beams. The generated OCT signals that are in turn interpretedby the control electronics to determine the spatial disposition of thestructures of interest in the patient's eye 43. The generated OCTsignals can also be interpreted by the control electronics to measurethe position and orientation of the patient interface 52, as well as todetermine whether there is liquid disposed between the posterior surfaceof the patient interface lens 96 and the patient's eye 43.

The OCT light source and detection device 98 works on the principle ofmeasuring differences in optical path length between the reference path106 and the sample path. Therefore, different settings of theZ-telescope 84 to change the focus of the UF laser beam do not impactthe length of the sample path for a axially stationary surface in theeye of patient interface volume because the optical path length does notchange as a function of different settings of the Z-telescope 84. Theranging subsystem 46 has an inherent Z range that is related to lightsource and the detection scheme, and in the case of frequency domaindetection the Z range is specifically related to the spectrometer, thewavelength, the bandwidth, and the length of the reference path 106. Inthe case of ranging subsystem 46 used in FIG. 3, the Z range isapproximately 4-5 mm in an aqueous environment. Extending this range toat least 20-25 mm involves the adjustment of the path length of thereference path 106 via a stage ZED within ranging subsystem 46. Passingthe OCT sample portion beam 102 through the Z-telescope 84, while notimpacting the sample path length, allows for optimization of the OCTsignal strength. This is accomplished by focusing the OCT sample portionbeam 102 onto the targeted structure. The focused beam both increasesthe return reflected or scattered signal that can be transmitted throughthe single mode fiber, and increases the spatial resolution due to thereduced extent of the focused beam. The changing of the focus of thesample OCT beam can be accomplished independently of changing the pathlength of the reference path 106.

Because of the fundamental differences in how the sample portion 102(e.g., 810 nm to 850 nm wavelengths) and the UF laser pulse beam 66(e.g., 1020 nm to 1050 nm wavelengths) propagate through the sharedoptics 50 and the patient interface 52 due to influences such asimmersion index, refraction, and aberration, both chromatic andmonochromatic, care must be taken in analyzing the OCT signal withrespect to the UF laser pulse beam 66 focal location. A calibration orregistration procedure as a function of X, Y, and Z can be conducted inorder to match the OCT signal information to the UF laser pulse beamfocus location and also to the relative to absolute dimensionalquantities.

There are many suitable possibilities for the configuration of the OCTinterferometer. For example, alternative suitable configurations includetime and frequency domain approaches, single and dual beam methods,swept source, etc., are described in U.S. Pat. Nos. 5,748,898;5,748,352; 5,459,570; 6,111,645; and 6,053,613.

The system 2 can be set to locate the anterior and posterior surfaces ofthe lens capsule and cornea and ensure that the UF laser pulse beam 66will be focused on the lens capsule and cornea at all points of thedesired opening. Imaging modalities and techniques described herein,such as for example, Optical Coherence Tomography (OCT), and such asPurkinje imaging, Scheimpflug imaging, confocal or nonlinear opticalmicroscopy, fluorescence imaging, ultrasound, structured light, stereoimaging, or other known ophthalmic or medical imaging modalities and/orcombinations thereof may be used to determine the shape, geometry,perimeter, boundaries, and/or 3-dimensional location of the lens andlens capsule and cornea to provide greater precision to the laserfocusing methods, including 2D and 3D patterning. Laser focusing mayalso be accomplished using one or more methods including directobservation of an aiming beam, or other known ophthalmic or medicalimaging modalities and combinations thereof, such as but not limited tothose defined above.

Optical imaging of the cornea, anterior chamber and lens can beperformed using the same laser and/or the same scanner used to producethe patterns for cutting. Optical imaging can be used to provideinformation about the axial location and shape (and even thickness) ofthe anterior and posterior lens capsule, the boundaries of the cataractnucleus, as well as the depth of the anterior chamber and features ofthe cornea. This information may then be loaded into the laser 3-Dscanning system or used to generate a three dimensionalmodel/representation/image of the cornea, anterior chamber, and lens ofthe eye, and used to define the cutting patterns used in the surgicalprocedure.

Observation of an aim beam can also be used to assist in positioning thefocus point of the UF laser pulse beam 66. Additionally, an aim beamvisible to the unaided eye in lieu of the infrared OCT sample portionbeam 102 and the UF laser pulse beam 66 can be helpful with alignmentprovided the aim beam accurately represents the infrared beamparameters. The alignment guidance subsystem 48 is included in theassembly 62 shown in FIG. 3. An aim beam 108 is generated by an aim beamlight source 110, such as a laser diode in the 630-650 nm range.

Once the aim beam light source 110 generates the aim beam 108, the aimbeam 108 is transmitted along an aim path 112 to the shared optics 50,where it is redirected by a beam combiner 114. After being redirected bythe beam combiner 114, the aim beam 108 follows a shared path with theUF laser pulse beam 66 through the shared optics 50 and the patientinterface 52. In this way, the aim beam 108 is indicative of thelocation of the UF laser pulse beam 66. The aim beam 108 passes throughthe Z-telescope 84, is redirected by the X-scan device 86 and by theY-scan device 88, passes through the beam combiner 90, passes throughthe objective lens assembly 94 and the patient interface 52, and on intothe patient's eye 43.

The video subsystem 92 is operable to obtain images of the patientinterface and the patient's eye. The video subsystem 92 includes acamera 116, an illumination light source 118, and a beam combiner 120.The video subsystem 92 gathers images that can be used by the controlelectronics 54 for providing pattern centering about or within apredefined structure. The illumination light source 118 can be generallybroadband and incoherent. For example, the light source 118 can includemultiple LEDs. The wavelength of the illumination light source 118 ispreferably in the range of 700 nm to 750 nm, but can be anything that isaccommodated by the beam combiner 90, which combines the light from theillumination light source 118 with the beam path for the UF laser pulsebeam 66, the OCT sample beam 102, and the aim beam 108 (beam combiner 90reflects the video wavelengths while transmitting the OCT and UFwavelengths). The beam combiner 90 may partially transmit the aim beam108 wavelength so that the aim beam 108 can be visible to the camera116. An optional polarization element can be disposed in front of theillumination light source 118 and used to optimize signal. The optionalpolarization element can be, for example, a linear polarizer, a quarterwave plate, a half-wave plate or any combination. An additional optionalanalyzer can be placed in front of the camera. The polarizer analyzercombination can be crossed linear polarizers thereby eliminatingspecular reflections from unwanted surfaces such as the objective lenssurfaces while allowing passage of scattered light from targetedsurfaces such as the intended structures of the eye. The illuminationmay also be in a dark-filed configuration such that the illuminationsources are directed to the independent surfaces outside the capturenumerical aperture of the image portion of the video system.Alternatively, the illumination may also be in a bright fieldconfiguration. In both the dark and bright field configurations, theillumination light source can be used as a fixation beam for thepatient. The illumination may also be used to illuminate the patient'spupil to enhance the pupil iris boundary to facilitate iris detectionand eye tracking. A false color image generated by the near infraredwavelength or a bandwidth thereof may be acceptable.

The illumination light from the illumination light source 118 istransmitted through the beam combiner 120 to the beam combiner 90. Fromthe beam combiner 90, the illumination light is directed towards thepatient's eye 43 through the objective lens assembly 94 and through thepatient interface 52. The illumination light reflected and scattered offof various structures of the eye 43 and patient interface 52 travel backthrough the patient interface 52, back through the objective lensassembly 94, and back to the beam combiner 90. At the beam combiner 90,the returning light is directed back to the beam combiner 120 where thereturning light is redirected toward the camera 116. The beam combinercan be a cube, plate or pellicle element. It may also be in the form ofa spider mirror whereby the illumination transmits past the outer extentof the mirror while the image path reflects off the inner reflectingsurface of the mirror. Alternatively, the beam combiner could be in theform of a scraper mirror where the illumination is transmitted through ahole while the image path reflects off of the mirrors reflecting surfacethat lies outside the hole. The camera 116 can be a suitable imagingdevice, for example but not limited to, any silicon based detector arrayof the appropriately sized format. A video lens forms an image onto thecamera's detector array while optical elements provide polarizationcontrol and wavelength filtering respectively. An aperture or irisprovides control of imaging NA and therefore depth of focus and depth offield and resolution. A small aperture provides the advantage of largedepth of field that aids in the patient docking procedure.Alternatively, the illumination and camera paths can be switched.Furthermore, the aim light source 110 can be made to emit infrared lightthat would not be directly visible, but could be captured and displayedusing the video subsystem 92.

FIG. 3B shows a mapped treatment region 182 (hatched area) of the eyecomprising the cornea 184, the posterior capsule 186, and the limbus188. The treatment region 182 can be mapped with computer modeling, forexample ray tracing and phased based optical modeling to incorporatefactors such as laser beam quality, pulse width, system transmission,numerical aperture, polarization, aberration correction, and alignment.The treatment volume 182 is shown extending along the Z-axis from theposterior surface of the optically transmissive structure of the patientinterface a distance of over 15 mm, such that the treatment volume 182includes the cornea 184, and the lens 190 in which the treatment volumeof the lens 190 includes the anterior capsule 192, the posterior capsule186, the nucleus and the cortex. The treatment volume 182 extendslaterally from the center of the cornea 184 to beyond the limbus 188.The lateral dimensions of the volume 182 are defined by a Y contour 194anterior to the limbus 188 and by an X contour 196 posterior to thelimbus 188. The treatment volume 182 shown can be determined by a personof ordinary skill in the art based on the teachings described herein.The lateral positions of predicted optical breakdown for ZL fixed to 30mm 198 and ZL fixed to 20 mm 199 are shown. These surfaces that extendtransverse to the axis 99 along the Z-dimension correspond to locationsof optical scanning of the X and Y galvos to provide optical breakdownat lateral locations away from the axis 99. The curved non-planar shapeof the scan path of optical breakdown for ZL-30 mm 198 and ZL-20 mm 199can be corrected with the mapping and LUTs as described herein. Thecurved shape of the focus can be referred to as a warping of the opticalbreakdown depth and the LUTs can be warped oppositely or otherwiseadjusted so as to compensate for the warping of the treatment depth, forexample. Additionally, the warping inherent in the prediction from themodel can be incorporated in the generic look-up table and any furthererror from this predicted form as indicated by measurement andapplication of a correction factor to offset this error may also becalled a warping of the look up table.

The treatment region 182 is shown for setting the laser beam energyabout four times the threshold amount for optical breakdown empiricallydetermined for a beam near the limbus of the system. The increasedenergy or margin above ensures that the beam system will be able totreat given variability in contributing factors. Theses contributingfactors may include degradation over lifetime of the laser with regardto energy, beam quality, transmission of the system, and alignment.

The placement of the posterior surface of the optically transmissivestructure of the patient interface away from the surface of the corneacan provide the extended treatment range as shown, and in manyembodiments the optically transmissive structure comprises the lens. Inalternative embodiments, the posterior surface of the opticallytransmissive structure can be placed on the cornea, for example, and themapping and LUTs as described here can be used to provide the patienttreatment with improved accuracy.

The optically transmissive structure of the patient interface maycomprise one or more of many known optically transmissive materials usedto manufactures lenses, plates and wedges, for example one or more ofglass, BK-7, plastic, acrylic, silica or fused silica for example.

The computer mapping of the treatment volume 182 may optionally beadjusted with mapping based on measurements of a constructed system asdescribed herein.

FIG. 4A shows correspondence among movable and sensor components of thelaser delivery system 2. The movable components may comprise one or morecomponents of the laser delivery system 2 as described herein. Themovable components of the laser delivery system may comprise the zoomlens capable of moving distance ZL, the X galvo mirror 96 capable ofmoving an angular amount Xm, and the Y galvo mirror 88 capable of movingan angular amount Ym. The movable components of the OCT system maycomprise the movable OCT reference arm configured to move the referencepath 106 a distance ZED. The sensor components of the laser system maycomprise the video camera having X and Y pixels, Pix X and Pix Y,respectively, and sensor components of the OCT system such as thespectral domain detection as described herein. The patient support whichmay comprise a bed is movable in three dimensions so as to align the eye43 of the patient P with laser system 2 and axis 99 of the system. Thepatient interface assembly comprises an optically transmissive structurewhich may comprise an interface lens 96, for example, configured to bealigned with system 2 and an axis of eye 43. The patient interface lenscan be placed on the patient eye 43 for surgery, and the opticallytransmissive structure can be placed at a distance 162 from theobjective lens 94. In many embodiments, the optically transmissivestructure comprises lens 96 placed a contact lens optical distance 162(hereinafter “CLopt”). The optically transmissive structure comprises athickness 164, and the thickness 164 may comprise a thickness of thecontact lens 96, for example. Although the optically transmissivestructure comprising contact lens 96 may contact the eye 2, in manyembodiments the contact lens 168 is separated from the cornea with gap168 extending between the lens and the vertex of the cornea, such thatthe posterior surface of the contact lens 168 contacts a solutioncomprising saline or a viscoelastic solution, for example.

FIG. 4B shows mapping of coordinate references from an eye spacecoordinate reference system 150 to a machine coordinate reference system151 so as to coordinate the machine components with the physicallocations of the eye. The laser system 2 can map physical coordinates ofthe eye 43 to machine coordinates of the components as described herein.The eye space coordinate reference system 150 comprises a first Xdimension 152, for example an X axis, a second Y dimension 154, forexample a Y axis, and a third Z dimension 156, for example a Z axis, andthe coordinate reference system of the eye may comprise one or more ofmany known coordinate systems such as polar, cylindrical or Cartesian,for example. In many embodiments the reference system 150 comprises aright handed triple with the X axis oriented in a nasal temporaldirection on the patient, the Y axis oriented superiorly on the patientand the Z axis oriented posteriorly on the patient. In many embodiments,the corresponding machine coordinate reference system 151 comprises afirst X′ dimension 153, a second Y′ dimension 155, and a third Z′dimension 157 generally corresponding to machine actuators, and thecoordinate reference system of the machine may comprise one or more ofmany known coordinate systems such as polar, cylindrical or Cartesian,and combinations thereof, for example.

The machine coordinate reference 151 may correspond to locations of oneor more components of system 2. The machine coordinate reference system151 may comprise a plurality of machine coordinate reference systems.The plurality of machine coordinate reference systems may comprise acoordinate reference system for each subsystem, for example. Forexample, dimension 157 may correspond to movement of the z-telescopelens capable of moving distance ZL. The dimension 153 may correspond tomovement of the X galvo mirror 86 capable of moving an angular amountXm, and the dimension 153 may correspond to movement of the Y galvomirror 88 capable of moving an angular amount Ym. Alternatively or incombination, the dimension 157 may correspond to movable OCT referencearm configured to move the reference path 106 a distance ZED, along withdimension 157 corresponding to a movement of the z-telescope for the OCTbeam, and the dimension 153 and the dimension 155 may correspond tomovement of the X galvo mirror 86 and the Y galvo mirror 88,respectively, for the OCT beam. The dimension 151 may correspond to Xpixels of the video camera and dimension 153 may correspond to Y pixelsof the video camera. The axes of the machine coordinate reference systemmay be combined in one or more of many ways, for example the OCTreference arm movement of the reference path 106 the distance ZED can becombined with movement of the z-telescope lens capable of moving thedistance ZL, for example. In many embodiments, the locations of thecomponents of the laser system 2 are combined when in order to map theplurality of machine coordinate reference systems to the coordinatereference system 150 of eye 43.

In many embodiments, the eye coordinate reference system is mapped froman optical path length coordinate system to physical coordinates of theeye based on the index of refraction of the tissues of the eye. Anexample is the OCT ranging system where measurements are based onoptical thicknesses. The physical distance can be obtained by dividingthe optical path length by the index of refraction of the materialthrough which the light beam passes. Preferable the group refractiveindex is used and takes into account the group velocity of the lightwith a center wavelength and bandwidth and dispersion characteristics ofthe beam train. When the beam has passed through more than one material,the physical distance can be determined based on the optical path lengththrough each material, for example. The tissue structures of the eye andcorresponding index of refraction can be identified and the physicallocations of the tissue structures along the optical path determinedbased on the optical path length and the indices of refraction. When theoptical path length extends along more than one tissue, the optical pathlength for each tissue can be determined and divided by thecorresponding index of refraction so as to determine the physicaldistance through each tissue, and the distances along the optical pathcan be combined, for example with addition, so as to determine thephysical location of a tissue structure along the optical path length.Additionally, optical train characteristics may be taken into account.As the OCT beam is scanned in the X- and Y-directions, and departurefrom the telecentric condition occurs due to the axial location of thegalvo mirrors, a distortion of the optical path length is realized. Thisis commonly known as fan error, and can be corrected for either throughmodeling or measurement.

As one or more optical components and light sources as described heremay have different path lengths, wavelengths, and spectral bandwidths,in many embodiments the group index of refraction used depends on thematerial and the wavelength and spectral bandwidth of the light beam. Inmany embodiments, the index of refraction along the optical path maychange with material. For example, the saline solution may comprise afirst index of refraction, the cornea may comprise a second index ofrefraction, the anterior chamber of the eye may comprise a third indexof refraction, and the eye may comprise gradient index lens having aplurality of indices of refraction. While optical path length throughthese materials is governed by the group index of refraction, refractionor bending of the beam is governed by the phase index of the material.Both, the phase and group index, can be taken into account to accuratelydetermine the X, Y, and Z location of a structure. While the index ofrefraction of tissue such as eye 43 can vary with wavelength asdescribed herein, approximate values include: aqueous humor 1.33; cornea1.38; vitreous humor 1.34; and lens 1.36 and 1.41, in which the index ofthe lens can differ for the capsule, the cortex and the nucleus, forexample. The phase index of refraction of water and saline can be about1.325 for the ultrafast laser at 1030 nm and about 1.328 for the OCTsystem at 830 nm. The group refractive index of 1.339 differs on theorder of 1% for the OCT beam wavelength and spectral bandwidth. A personof ordinary skill in the art can determine the indices of refraction andgroup indices of refraction of the tissues of the eye for thewavelengths of the measurement and treatment systems as describedherein. The index of refraction of the other components of the systemcan be readily determined by a person of ordinary skill in the art basedon the teachings described herein.

FIGS. 5A-5F show a topography measurement structure configured to coupleto a patient interface 52 as described here to measure the eye prior tothe eye contacting the patient interface. The topography measurementstructure may comprise one or more of a ring or other structure for akeratometry reading of the eye, a Placido disc topography of the eye, areflection of a plurality of points from the cornea topography of theeye, a grid reflected from the cornea of the eye topography. In manyembodiments, the measurement structure comprises a Placido discstructure configured to couple to a component of the patient interface,for example. The topography measurement structure can be illuminated,for example, so as to form a virtual image of the measurement structurewhen reflected from the cornea. One illumination strategy could make useof the internal existing illuminator of the system itself. Alternativelyor in combination, the topography structure may comprise a ringilluminator either mounted to the patient interface or to the structureof the laser system.

One embodiment of the topography measurement structure is shown forinstance in FIG. 5A. The topography measurement structure 195 generallycomprises a first end 204 to be brought into a proximal position to apatient's eye and a second end 200 opposite the first end that isconfigured for attaching to the patient interface. The first end 204generally comprises one or more geometric markers 206 that will be usedfor blink detection of the patient's eye. In a preferred embodiment, thesame geometric markers 206 may also be used for measurement of thecorneal topography. This is, however, not strictly required. The firstend may comprise one or more geometric markers for blink detection andone or more different geometric structures for topography measurement.The first end also comprises an aperture 202 that allows light to passthrough the first end 204 of the topography measurement structure 195.Another embodiment of the topography measurement structure 195 accordingto the present invention is shown, for instance, in FIGS. 5D, 5E and 5F.

The specific shape of the geometric marker at the first end 204 is notparticularly limited. Preferably, the geometric marker includes at leastone circle. In another embodiment, the geometric marker comprises two ormore concentric circles. Other permissible geometric permissiblegeometric markers include lines and ovals.

In many embodiments, topography measurement structure including thegeometric marker 206 is back illuminated with light from the lasersystem to illuminate the eye with the geometric marker 206.Alternatively or in combination the topography measurement structure 195may comprise a plurality of light sources (not shown) such as lightemitting diodes to illuminate the eye with the topography measurementstructure 195 including the geometric marker 206.

FIG. 5B shows the topography measurement structure 195 including one ormore geometric marker removably coupled to the patient interface toposition the topography measurement structure 195 in relation to the eyewhen the patient has been placed on the support of the laser eye surgerysystem as described herein. An OCT beam is shown passing throughaperture 202 of the topography measurement structure 195, which permitsOCT measurements to be mad simultaneously and in conjunction with thetopography measurement structure 195.

The OCT measurement beam can be used to position the eye. This use ofthe OCT measurement beam may be particularly important to achieveabsolute curvature readings of the Placido system as the diameter of thereflected Placido rings may depend not only on the curvature of thecornea but also from the distance of the ring illuminator and thecornea. OCT can help to minimize these variations. Additionally, thismeasurement information can also be used to actively track position thepatient's chair and move the eye into the correct or desired position.Additionally, the OCT system and optionally also the camera can be usedto locate the actual position of the concentric rings in relation to thesystem to enable high precision measurements. Alternatively or incombination, the focus of the video camera as describe here can be usedto position the eye for measurement. When the topography of the patienthas been measured and the axis determined, for example, the topographymeasurement system can be decoupled from the patient interface structureand the patient interface coupled to the eye as described herein.

The illuminator can be constructed in many different ways. Having aclear aperture in the center of the ring structure to allow the videosystem to be used as is may be particularly important. Other embodimentsmay comprise a combination of different engineered diffusers and maskswhich can be optimized on the diffusing angle used to the detection ofthe rings from the cornea. Or, if polarized light is used, a combinationof quarter wave plate or depolarizer and diffuser with ring aperturescan be used. For full utilization, the light illuminated on the blockedrings can make the blocked rings act as reflecting wedges so the lightis fully utilized. In such cases, an angle which enables totalreflection may be helpful. Utilizing a combination of a strong negativelens and the Placido disk illuminator can also increase the lightintensity of the outer rings for better contrast.

In many embodiments, the topography measurement structure comprises anexternal illumination structure such as a ring illuminator illuminatesthe eye to form a ring shaped virtual image of the illuminationstructure, and the astigmatic axis of the eye determined based onmeasurements of the virtual image of the eye as described herein. Theexternal illuminator can be configured to couple to the patientinterface for measurement of the eye and removed when the eye has beendocked to the patient interface. Alternatively, the external illuminatormay comprise a substantially fixed structure that remains fixed to thelaser system throughout a plurality of procedures.

The corneal topography data and thickness data can be combined in one ormore of many ways. For example, the corneal topography data can be usedto determine the shape profile of the anterior corneal surface, and thecorneal thickness profile data can be fit to the anterior cornealsurface profile in order to determine the profile of the posteriorsurface, for example. In many embodiments, the anterior corneal surfaceprofile is measured and determined without the patient interfacecontacting the eye, and the corneal thickness profile is measured anddetermined when the patient interface contacts the eye. The cornealsurface profile data measured without contacting the eye can be combinedwith the corneal thickness profile data measured with the patientinterface contacting the eye, and the location of refractive incisionsdetermined in response to both profiles, for example.

As illustrated in FIG. 5C, light reflected by the cornea is generallymeasured at discrete points, preferably along multiple radial lines todetermine the existence and nature of the virtual image formed whenlight is reflected off the cornea.

FIG. 5D shows components of the patient interface and the topographymeasurement structure configured to couple to the patient interface.

FIG. 6 shows a flow chart for performing a method of blink detection 600in a laser eye surgical system. The method includes providing atopography measurement structure having at least one geometric markerand placing the topography measurement structure into a positionproximal to an eye of a patient such that light traveling from the atleast one geometric marker is capable of reflecting off a refractivestructure of the eye of the patient (Act 602). A detecting step includesdetecting the light reflected from the eye of the patient for apredetermined time period while the topography measurement structure isat the proximal position (Act 604). The method includes converting thelight reflected from the surface of the eye in the predetermined timeperiod into image data (Act 606) and analyzing the image data todetermine whether light from the geometric marker is detected in thereflected light (Acts 608 and 610). If the geometric marker isdetermined not to be present in the reflected light, the patient isidentified as having blinked during the predetermined time (Act 612). Ifthe geometric marker is determined to be present in the reflected light,the patient is determined to not have blinked during the predeterminedtime period.

The patient's eye may be positioned proximal to an eye of a patient suchthat light traveling from the at least one geometric marker is capableof reflecting off a refractive structure of the eye of the patientwithin the capture range of the measurement system of the laser eyesurgery system as described herein, such as shown in FIG. 2. In manyembodiments, positioning of the patient for laser surgery is typicallyenabled by motion of the patient bed 34 or by motion of the laser system2. Typically, the operator has manual control of the lateral and axialposition, guiding the docking mechanism or patient interface 52 intoplace in a step 528. In the absence of a docking mechanism, an operatormeans for guiding the motion so that the eye, and specifically thecornea, is placed within the operative range of the measurement systemmay be provided. This can be accomplished with the use of subsystems ofthe laser system 2 described here such as alignment guidance system 48of laser system 2 or imaging subsystem 51. Initial patient position canbe guided by a video camera, guiding the eye into lateral position bycentering the video image, and into axial position by focusing theimage.

In the detecting step, light reflected from the eye of the patient isdirected to a detector through a predetermined optical path. Thepropagation of the reflected light to the detector may be achieved inmany ways. In many embodiments, the reflected light is directed byshared optics 50 of the laser system of FIGS. 2 and 3A. In oneembodiment, illumination light from the illumination light source 118 istransmitted through the beam combiner 120 to the beam combiner 90 and isdirected towards the patient's eye 43 through the objective lensassembly 94 and through the patient interface 52, which includes atopography measurement structure having the one or more geometricmarkers 206. The illumination light is then scattered off of cornea ofthe eye 43 and patient interface and travels back through the patientinterface 52, back through the objective lens assembly 94, and back tothe beam combiner 90. At the beam combiner 90, the returning light isdirected back to the beam combiner 120 where the returning light isredirected toward the camera 116. Alternatively, the illumination andcamera paths can be switched.

The manner in which the reflected light is converted into image data isnot particularly limited. For instance, the reflected light may bedirected to photodetector. The type of image data, including the datatype and format, that may be used in connection with the methods of thepresent invention is not particularly limited. The data is preferablypixel data.

Once the reflected light is converted into image data, it must beanalyzed for the presence of a shape corresponding to the shape ofgeometric marker 206. A preferred embodiment is to use the HoughTransfer to detect geometric marker 206 within the image data. Oneadvantage of the Hough transform technique is that it is tolerant ofgaps in feature boundary descriptions and is relatively unaffected byimage noise.

The Hough transform can be used to analyze the image data to identifyand isolate geometric marker 206 within the image. The Hough transformis generally used for the detection of regular curves such as lines,circles, ellipses, etc., and thus, is particularly-suited when geometricmarkers 206 in the form of lines and circles are selected. Although ageneralized Hough transform may be employed in applications where asimple analytic description of geometric marker 206 is not possible,computational complexity and speed are limiting factors in the use of ageneralized Hough algorithm. Therefore, in a preferred embodiment,analysis using the Hough transform should generally be limited toregular curves, and especially lines, circles and ellipses. The use ofthe Hough transform to detect ellipses may be particularly suitable inthe case of astigmatic eyes, in which circular forms may be reflectedoff a patient's eye as ellipses. But, even in the case of astigmatic orother non-standard shaped eyes, the reflected shape of a circular formis sufficiently circular that the Hough transform for circles issuitably accurate for detecting a blink of the patient's eye.

As would be understood by those of ordinary skill, the Hough transformidentifies the parameter(s) of a curve which best fits a set of givenedge points. The edges may be obtained from a known feature detectingoperator such as the Roberts Cross, Sobel or Canny edge detector and maybe noisy, i.e. it may contain multiple edge fragments corresponding to asingle whole feature. The output of an edge detector defines wherefeatures are in an image. The Hough transform determines what thefeatures are (i.e. it detects the feature(s) for which it has aparametric (or other) description) and how many of them exist in theimage.

Where the geometric marker 206 is one or more circles, the Houghtransform can be used to determine the presence and parameters of acircle or circles, if any, that are present in image data when a numberof points that fall on the perimeter are known. A circle with radius Rand center (a,b) can be described with the parametric equations

x=a+R cos(t)

y=b+R sin(t),

when the angle t sweeps through the full 360 degree range the points(x,y) trace the perimeter of a circle.

When the image data corresponding to the reflected image from the eyecontains sufficient points, some of which fall on perimeters of circles,the Hough Transform finds parameter triplets (a,b,R) to describe eachcircle present in the image data, thus determining the presence oflight, if any, corresponding to geometric marker 206 in the image data.

Preferably, the radius of geometric marker 206 is known radius R. If thecircles in an image are of known radius R, the locus of (a,b) points inthe parameter space fall on a circle of radius R centered at (x,y). Thetrue center point will be common to all parameter circles, and can befound with a Hough accumulation array. In this case, the presence orabsence of the geometric marker 206 in the image data can be determinedwith reference Hough accumulation array, and particularly thedetermination of whether accumulation array has a true center.Alternatively, the search for circles with unknown radius can beconducted by using a three dimensional accumulation matrix. When theHough Transform identifies the presence of the geometric marker in imagedata, the eye is determined to be open, and it is determined that thepatient did not blink. When the Hough Transform does not find thepresence of the geometric marker in the image data, the eye isdetermined to be closed, and it is determined that the patient blinked.

When the Hough Transform is used to analyze the image data,pre-processing of the image data, such as smoothing of the image data ispreferably performed.

Alternative data analysis to the Hough Transform for detection ofgeometric marker 206 in the image data include fitting circles andmeasuring the goodness of fit or image correlation with a template ofthe same shape as geometric marker 206.

FIG. 7A shows image data of a geometric marker 206 in the case where thegeometric marker 206 is two concentric circles. FIG. 7B shows theresults of the circular Hough transform in parameter space (a,b). FIG.7B shows a region of high intensity, or a “hotspot” corresponding to atrue center in the accumulation array, thus indicating the presence of acircular geometric marker in the image data. Based on presence of the“hotspot,” i.e. a true center in the accumulation array, it isdetermined that the eye did not blink at the time the reflected lightfrom the cornea was detected.

In the blink detection method and system of the present invention, thetime period over which the image data is collected is not particularlylimited. Collection of the image data may begin immediately when thetopography measurement structure is placed proximal to the eye of thepatient or at any subsequent point at the discretion of the operator.For blink detection, the reflected light is detected during a discretepredetermined time period, and the detected reflected light for thattime period is converted to image data. The reflected light ispreferably periodically re-measured, and the reflected lightcorresponding to each time period is preferably converted to image dataand preferably stored in memory. In this manner, the occurrence ofpatient blinking over time may be collected in stored in memory. Thecollected data may be used at later time to identify which

The predetermined time period during which reflected light is detectedshould generally be long enough to allow for sufficient light to bemeasured by the detector system but should be short enough to resolve ablink of an eye. The blink of an eye is estimated to take up to 100 to400 milliseconds. The predetermined time period for measurement ispreferably less than 400 milliseconds, more preferably less than 100milliseconds. Preferably, the reflected light is preferably periodicallyre-measured at a rate of at least 2 Hz, more preferably at least 10 Hz,more preferably at least 20 Hz, and even more preferably 30 Hz or more.

FIGS. 8A and 8B illustrate a blink detection and corneal topographymethod and system according to many embodiments of the invention. FIG.8A illustrates the operation of the corneal topography and blinkdetection system when the eye is open. FIG. 8B illustrates the operationof the corneal topography and blink detection system when the eye isclosed.

In FIG. 8A, the topography measurement structure including the geometricmarker 206 is arranged in a position proximal to the eye 43 of thepatient such that light originating from the at least one geometricmarker 206 is capable of reflecting off the cornea 44 of the patient'seye when lid 45 is open. The geometric marker 206 is illuminated and alight pattern 208 corresponding to the geometric marker 206 is directedfrom the first end of the topography measurement structure to the eye 43of the patient. The light reflected from the patient's eye forms avirtual image 210 that is directed by the shared optics 50 to a detector121, is converted to image data in the form of pixel data, Pix X and PixY, and is displayed via camera 116. The image data is then analyzed todetermine whether light corresponding to the virtual image 210 havingthe shape of geometric marker 206 was detected by the detector 121.Specifically, in FIG. 8A, the geometric marker 206 is in the shape ofconcentric circles, and as such, the image data is analyzed (by, forexample, the Hough transform) to determine whether a circle is presentin the image data. If the image data is determined to include the shapeof the geometric marker, than it is determined that the patient did notblink (i.e., the patient's eye was open). In a preferred embodiment, avisual indication 122, corresponding for example to the location of atrue center in parameter space, is provided on camera 116 indicatingthat the patient did not blink.

In FIG. 8B, the patient's eye lid 45 is closed and thus covers the topsurface of the cornea 44. As in FIG. 8A, the topography measurementstructure, including the geometric marker 206 is arranged in a positionproximal to the eye 43 of the patient such that light originating fromthe at least one geometric marker 206 is capable of reflecting off thecornea 44 of the patient's eye when lid 45 is open. Further, thegeometric marker 206 is illuminated and a light pattern 208corresponding to the geometric pattern 26 is directed from the first endof the topography measurement structure to the eye 43 of the patient.However, the surface of the eyelid and the eye lash (not shown) do notefficiently reflect light and the light is scattered of the lid, suchthat no virtual image of the geometric marker 206 is formed in the lightdirected by the shared optics to the detector 121. The light detected bythe detector 121 is converted to image data in the form of pixel data,Pix X and Pix Y, and is displayed via camera 116. The image data is thenanalyzed to determine whether light corresponding to the virtual image210 having the shape of geometric marker 206 was detected by thedetector 121. Specifically, in FIG. 6A, the geometric marker 206 is inthe shape of a circle, and as such, the image data is analyzed todetermine whether a circle is present in the image data. If the imagedata is determined to not include the shape of the geometric marker,than it is determined that the patient did not blink (i.e. the patient'seye was open). Although not shown in the Figure, a visual indication maybe provided indicating that the patient blinked.

As shown in FIG. 5B, aperture 202 in the first end 204 of the topographymeasurement structure permits other light based measurements andprocedures, such as an OCT measurement beam to pass through thetopography measurement structure 109. The blink detection methods andsystems of FIGS. 5-8 thus may be concurrently with other techniquesdesigned to measure the structure or position of the eye. The nature ofthe concurrent measurement is not particularly limited and may generallybe any measurement directed to generating structural or position data ofthe eye of the patient, including ranging, corneal topography,tomography, and laser surgical eye procedures.

In many embodiments, the blink detection methods described here willcorrelate in time with other measurements, or actions taken by thesurgical system. This may be accomplished for instance, by detectingreflected light from the geometric pattern 206 at predetermined timeperiods during the time period one or more other measurements is carriedout so that blink detection and the other measurement, and theirrespective data, are both performed and stored the same time, T, in themeasurement process. When blink detection is carried out concurrentlywith another structural or position measurement, blink detection may beshown in “real time,” that is, as the concurrent measurement is beingcarried out. The image data may also be stored for later analysis orprocessing to determine whether a blink occurred during at least aportion of the time the concurrent measurement was taken. If a blink isdetected during the concurrent measurement, the concurrent measurementmay be re-done. Alternatively, data corresponding from the concurrentmeasurement at times a blink is determined to have occurred may beeliminated from further use in data processing or analysis during anypost-processing.

A method of improved imaging and ranging in a laser eye surgical system,comprises providing a topography measurement structure having at leastone geometric marker into a position proximal to an eye of a patientsuch that light traveling from the at least one geometric marker iscapable of reflecting off a refractive surface of the eye of thepatient. The refractive surface is preferably the cornea, and may be thetear film of the cornea. The method includes generating structural orposition data regarding an eye of a patient, and during at least aportion of the generating step and while the topography measurementstructure is at the proximal position, periodically detecting the lightreflected from the refractive structure of the eye of the patient for apredetermined period of time. The method further includes converting thelight reflected from the surface of the eye for at least onepredetermined time period into image data; and analyzing the image datato determine whether the geometric marker was present in the reflectedlight, wherein if the geometric marker is determined not to be present,the patient is determined to have blinked during the predetermined time.if the geometric marker is determined to be present, the patient isdetermined not to have blinked during the predetermined time

The method further comprising re-generating the structural or positioninformation regarding the eye of the patient if the patient wasdetermined to have blinked during the eye measure. Alternatively, themethod includes identifying that the structural or position datacorresponding to the time periods during which the patient has beendetermined to have blinked are not accurate, and preferably removingstructural or position data corresponding to the time periods duringwhich the patient has been determined to have blinked.

In many embodiments, the least one geometric marker comprises a circle.Alternatively, there is a plurality of geometric markers, and theplurality of geometric markers comprises at least two concentriccircles.

The step of analyzing the image data comprises performing at least oneof a Hough transform of the image data, fitting the image data andmeasuring a goodness of fit, and image correlation with geometric markertemplate. In many embodiments, the Hough Transform is selected.

FIG. 9 shows a flow chart of a method 500 for providing accurate anddistortion-free corneal topography measurement and subsequentintegration with the laser treatment, according to embodiments. Theblinking detection method and system described here may beadvantageously used concurrently with many aspects of the cornealtopography and laser treatments. The method 500 comprises the followingmain steps. In a step 525, the patient's eye is positioned within thecapture range of the measurement system of the laser eye surgery system2 or 2A described herein. In a step 550, the measurement system is usedto measure corneal shape with high accuracy. Such a measurement systemmay comprise the ranging subsystem 46 described above. In a step 575,any changes in the patient eye orientation that may occur between themeasurement time and the laser treatment time is accounted for inpost-processing.

Positioning step 525: In the step 525, the patient's eye is positionedwithin the capture range of the measurement system of the laser eyesurgery system as described herein, such as shown in FIGS. 2 and 3A, forexample. Positioning of the patient for laser surgery is typicallyenabled by motion of the patient bed 34 or by motion of the laser system2. Typically, the operator has manual control of the lateral and axialposition, guiding the docking mechanism or patient interface 52 intoplace in a step 528. In the absence of a docking mechanism, an operatormeans for guiding the motion so that the eye, and specifically thecornea, is placed within the operative range of the measurement systemmay be provided. This can be accomplished with the use of subsystems ofthe laser system 2 described here, such as alignment guidance system 48of laser system 2, or imaging subsystem 51. Initial patient position canbe guided by a video camera, guiding the eye into lateral position bycentering the video image, and into axial position by focusing theimage. At this point, the cornea is placed within the capture range ofthe OCT system of the ranging subsystem 46 or imaging subsystem 51,typically X mm to Y mm axially, in a step 531. The OCT system can beused to measure the axial position of the cornea in a step 534, and asuitable display provides the operator guidance for final, accuratepositioning. Alternatively, a visual imaging system such as a camera, acamera coupled to a microscope which may share optics with the lasersystem 2 or 2 a, a CCD, among others may be used instead of the OCTsystem to facilitate the positioning step 525.

The blink detection and methods described here are preferably usedconcurrently with the OCT measurement beam to detect the occurrence ofblinks during the positioning measurement. This concurrent use of theOCT measurement and blink detection may be particularly important toachieve absolute curvature readings of the Placido system, as thediameter of the reflected Placido rings may depend not only on thecurvature of the cornea, but also on the distance of the ringilluminator and the cornea. OCT and blink detection can help to minimizethese variations. Additionally, this measurement information can also beused to actively track position the patient's chair and move the eyeinto the correct or desired position. In connection with any of theseuses, the blink detection method and system may be used concurrently toidentify any blinking during the OCT measurement, especially duringcritical OCT measurements. As a result, the measurement can be re-done.Alternatively, the measurement data corresponding to the blink can beeliminated from data processing and measurement calculations.

Since the video and OCT systems are typically configured to operate withthe docking system, which often has additional optical elements andliquid medium in the optics path, the focusing algorithms of the lasersystem may be adjusted to account for operation without the dockingmechanism optics and interface medium.

Measurement step 550: In the step 550, the measurement system is used tomeasure corneal shape with high accuracy. The laser system 2 or 2Acomprises a subsystem for mapping the ocular surfaces that are beingtreated such as the ranging subsystem 46 having an OCT system describedhere, or the imaging subsystem 51. As described below, the imagingsubsystem 51 may apply other modalities for mapping the ocular surfacessuch as Placido imaging, Hartmann-shack wavefront sensing, confocaltomography, low coherence reflectometry, among others. The measurementstep 550 can be performed once the eye is positioned correctly in thestep 525 above. A fixation light can optionally be introduced to helpthe patient keep the eye pointed at a fixed angle. If the measurementdata capture is sufficiently fast, for example, on the order of onesecond, a fixation light may not be necessary. In a step 553 ofmeasurement 550, multiple OCT or other scans of the cornea surfaces canbe acquired in a short time. Multiple scans can increase the confidenceof obtaining good data. In a step 556, post-processing of the scans canremove potential eye motion and further improve the measurementaccuracy. In a step 562 of measurement step 550, corneal power can bemeasured from camera images of reflected light from the cornea.

Once the cornea surfaces have been mapped, polynomial, or other fittingalgorithms can be used to calculate commonly used parameters of thecornea in a step 559. Commonly used parameters include the optical powerof the cornea, astigmatic axis angle, and astigmatism magnitude.

The blink detection and methods described here are preferably usedconcurrently with the measurement of the corneal shape to detect theoccurrence of blinks during the measurement. This concurrent use of thecorneal shape measurement and blink detection allows for thedetermination of whether a blink has occurred during the measurement. Asa result, the measurement can be re-done. Alternatively, the measurementdata corresponding to the blink can be eliminated from data processingand fitting calculations.

Coordinate system transfer step 575: In the step 575, any changes in thepatient eye orientation that may occur between the measurement time andthe laser treatment time is accounted for. Often times, it is probablethat when the patient eye is docked for treatment such as with thesuction ring of the patient interface 52, the eye, including its variousanatomical features, will change its position relative to the lasersystem coordinates. This change can be a result of patient headmovement, eye movement, or because of force applied during docking. Insome cases, the refractive properties of the air or any liquid over theeye can distort the images of the eye. For example, the suction ring ofthe patient interface 52 may be filled with one or more of a solution,saline, or a viscoelastic fluid. It can be helpful to transform thecorneal measurements, like the astigmatic axis angle, to a newcoordinate system to account for any movement and distortion. Severalmeans for accomplishing this are provided.

In some embodiments, the operator can mark the patient eye prior to themeasurement with ink dots that are typically positioned diametricallyacross on the periphery of the cornea in a step 578. These dots can beacquired by the imaging camera after docking for treatment and used forcalculating the coordinate transformation in a step 581.

In other embodiments, ocular features that are visible in the videoimages, or in the OCT images or other scans taken during the measurementstep are used. These features are correlated to the images taken afterdocking for treatment in a step 584. This correlation can be performedby digital image processing algorithms, or manually by the operator.When performed manually, the operator is presented by overlapped images(measurement and treatment steps) on the control screen, and the imagesare manually manipulated in translation and rotation until they arevisibly matched. The image manipulation data can be detected by thedisplay software and used for the coordinate transform.

Although the above steps show method 500 of providing accurate anddistortion-free corneal topography measurement and subsequentintegration with the laser treatment according to many embodiments, aperson of ordinary skill in the art will recognize many variations basedon the teaching described herein. The steps may be completed in adifferent order. Steps may be added or deleted. For example, the shapeof the cornea may be measures before, during, or after docking fortreatment such as with a suction ring of the patient interface 52. Manyof the steps may be repeated as often as beneficial to the method.

One or more of the steps of the method 500 may be performed with thecircuitry as described herein, for example, one or more the processor orlogic circuitry such as the programmable array logic for fieldprogrammable gate arrays. The circuitry may be programmed to provide oneor more of the steps of method 500, and the program may comprise programinstructions stored on a computer readable memory or programmed steps ofthe logic circuitry such as the programmable array logic or the fieldprogrammable gate array, for example.

The blink detection system and method described here are preferably usedin connection with one or more of the Positioning Step 525 andMeasurement Step 550 in the method 500. Referring to FIG. 2, in thelaser eye surgery system 2, the OCT system of the ranging subsystem 46may be used to position the patient eye in the step 525 and/or tomeasure the shape of the cornea in the step 550. For the laser eyesurgery system 2, the topography measurement structure 53 is used tomeasure the shape of the cornea in the step 550. The shape of the corneacan be measured before, during, or after the patient interface 52 isdocked with the eye of the patient. Images captured by the rangingsubsystem 46 of the laser eye surgery system 2 or the imaging subsystem51 of the laser eye surgery system 2 and the corneal topographer 53 maybe displayed with a display of the control panel/GUI 56 of the laser eyesurgery system 2 or the display 56A of the laser eye surgery system 2A,respectively. The control panel/GUI 56 may also be used to modify,distort, or transform any of the displayed images.

All patents and patent applications cited here are hereby incorporatedby reference hereby reference in their entirety.

Further, the subject matter of the present disclosure is related to thefollowing patent applications: U.S. application Ser. No. 12/048,182,filed Mar. 3, 2008, entitled “METHOD AND APPARATUS FOR CREATINGINCISIONS TO IMPROVE INTRAOCULAR LENS PLACEMENT,” U.S. application Ser.No. 12/048,186, filed Mar. 13, 2008, entitled “METHOD AND APPARATUS FORCREATING OCULAR SURGICAL AND RELAXING INCISIONS,” U.S. application Ser.No. 14/069,703, filed Nov. 1, 2013, entitled “LASER EYE SURGERY SYSTEMCALIBRATION,” U.S. application Ser. No. 14/256,307, filed Apr. 18, 2014,entitled “CORNEAL TOPOGRAPHY MEASUREMENT AND ALIGNMENT OF CORNEALSURGICAL PROCEDURES,” U.S. patent application Ser. No. 14/199,087, filedMar. 6, 2014, entitled “MICROFEMTOTOMY METHODS AND SYSTEMS,” U.S. Ser.No. 14/255,430, filed Apr. 17, 2014, entitled “LASER FIDUCIALS FORALIGNMENT IN CATARACT SURGERY,” and U.S. patent application Ser. No.14/069,703; filed Nov. 1, 2013, entitled “LASER EYE SURGERY SYSTEMCALIBRATION.” The entire disclosures of the above applications areincorporated here by reference, and are suitable for combination withand according to the embodiments disclosed in this application.

The methods and apparatus as described here are suitable for combinationwith one or more components of laser eye surgery systems that are underdevelopment or commercially available such as: the adaptive patientinterface is described in Patent Cooperation Treaty Patent Application(“PCT”) PCT/US2011/041676, published as WO 2011/163507, entitled“ADAPTIVE PATIENT INTERFACE”; the device and method for aligning an eyewith a surgical laser are described in PCT/IB2006/000002, published asWO 2006/09021, entitled “DEVICE AND METHOD FOR ALIGNING AN EYE WITH ASURGICAL LASER”; the device and method for aligning an eye with asurgical laser are described in PCT/IB2006/000002, published as WO2006/09021, entitled “DEVICE AND METHOD FOR ALIGNING AN EYE WITH ASURGICAL LASER”; the apparatus for coupling an element to the eye isdescribed in U.S. application Ser. No. 12/531,217, published as U.S.Pub. No. 2010/0274228, entitled “APPARATUS FOR COUPLING AN ELEMENT TOTHE EYE”; and the servo-controlled docking force device for use inophthalmic applications is described in U.S. application Ser. No.13/016,593, published as U.S. Pub. No. US 2011/0190739, entitled “SERVOCONTROLLED DOCKING FORCE DEVICE FOR USE IN OPHTHALMIC APPLICATIONS.” Theentire disclosures of the above applications are incorporated here byreference and are suitable for combination with and according to theembodiments disclosed in this application.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated here or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. The term “connected” is to beconstrued as partly or wholly contained within, attached to, or joinedtogether, even if there is something intervening. Recitation of rangesof values here are merely intended to serve as a shorthand method ofreferring individually to each separate value falling within the range,unless otherwise indicated herein, and each separate value isincorporated into the specification as if it were individually recitedherein. All methods described here can be performed in any suitableorder unless otherwise indicated here or otherwise clearly contradictedby context. The use of any and all examples, or exemplary language(e.g., “such as”) provided herein, is intended merely to betterilluminate embodiments of the invention, and does not pose a limitationon the scope of the invention unless otherwise claimed. No language inthe specification should be construed as indicating any non-claimedelement as essential to the practice of the invention.

While certain illustrated embodiments of this disclosure have been shownand described in an exemplary form with a certain degree ofparticularity, those skilled in the art will understand that theembodiments are provided by way of example only, and that variousvariations can be made without departing from the spirit or scope of theinvention. Thus, it is intended that this disclosure cover allmodifications, alternative constructions, changes, substitutions,variations, as well as the combinations and arrangements of parts,structures, and steps that come within the spirit and scope of theinvention as generally expressed by the following claims and theirequivalents.

1-23. (canceled)
 24. A method, comprising: providing to an eye of apatient a light pattern produced by one or more geometric markers of acorneal topography measurement structure; for each of a plurality oftime periods: detecting light returned from the eye of the subject whileproviding the light pattern to the eye, converting the light returnedfrom the eye into corresponding image data, analyzing the image data todetermine whether the light pattern is present in the detected light,when it is determined that the light pattern is present in the detectedlight, using at least a portion of the image data corresponding to thelight pattern to make a corneal topography measurement of a cornea ofthe eye of the subject, and when it is determined that the light patternis not present in the detected light, determining that the subjectblinked and excluding the image data from the corneal topographymeasurement of the eye of the subject.
 25. The method of claim 24,wherein the light pattern includes at least one circular portion. 26.The method of claim 24, wherein the light pattern includes at least twoconcentric circular portions.
 27. The method of claim 24, wherein whenthe light pattern is present in the detected light, the light isreflected from the cornea.
 28. The method of claim 27, wherein the lightis reflected from the tear film of the cornea.
 29. The method of claim24, wherein the step of analyzing the image data comprises at least oneof: performing a Hough transform of the image data, fitting the imagedata and measuring a goodness of fit, and performing image correlationwith at least one geometric marker template.
 30. The method of claim 29,wherein the step of analyzing the image data comprises performing theHough transform of the image data.
 31. The method of claim 24, whereinthe time periods occur at a rate of 30 per second.
 32. A method,comprising: providing to an eye of a patient a light pattern produced byone or more geometric markers of a corneal topography measurementstructure; generating an optical coherence tomography (OCT) measurementbeam; passing the OCT measurement beam through the corneal topographymeasurement structure to the eye; for a given time period: obtaining OCTdata for a structure of the eye using the OCT measurement beam,detecting light returned from the eye of the subject while providing thelight pattern to the eye and passing the OCT measurement beam throughthe corneal topography measurement structure to the eye, converting thelight returned from the eye into corresponding image data, analyzing theimage data to determine whether the light pattern is present in thedetected light, when it is determined that the light pattern is presentin the detected light, using at least a portion of the image datacorresponding to the light pattern to make a corneal topographymeasurement of a cornea of the eye of the subject, and using the OCTdata to make an OCT measurement of the structure of the eye, and when itis determined that the light pattern is not present in the detectedlight, determining that the subject blinked and not using the image datafrom the corneal topography measurement of the eye of the subject tomake the corneal topography measurement of a cornea of the eye of thesubject, and not using the OCT data to make the OCT measurement of thestructure of the eye.
 33. The method of claim 32, wherein the lightpattern includes at least one circular portion.
 34. The method of claim32, wherein the light pattern includes at least two concentric circularportions.
 35. The method of claim 32, wherein when the light pattern ispresent in the detected light, the light is reflected from the cornea.36. The method of claim 35, wherein the light is reflected from the tearfilm of the cornea.
 37. The method of claim 32, wherein the step ofanalyzing the image data comprises at least one of: performing a Houghtransform of the image data, fitting the image data and measuring agoodness of fit, and performing image correlation with at least onegeometric marker template.
 38. The method of claim 37, wherein the stepof analyzing the image data comprises performing the Hough transform ofthe image data.
 39. The method of claim 32, wherein the structure of theeye is the cornea.
 40. A system, comprising: a corneal topographymeasurement structure having one or more geometric markers andconfigured to provide to an eye of a patient a light pattern produced bythe one or more geometric markers; an image capture device configured todetect light returned from the eye of the subject while providing thelight pattern to the eye and to generate image data therefrom; andcontrol electronics configured to control the image capture device toperiodically capture image data during each of a plurality of timeperiods when the corneal topography measurement structure provides thelight pattern to the eye, and to analyze the image data to determinewhether the light pattern is present in the detected light, and: whenthe control electronics determines that the light pattern is present inthe detected light during one of the time periods, using at least aportion of the image data, corresponding to the light pattern, for thatone time period to make a corneal topography measurement of a cornea ofthe eye of the subject, and when the control electronics determines thatthe light pattern is not present in the detected light during the one ofthe time periods, determining that the subject blinked and excluding theimage data for that one time period from the corneal topographymeasurement of the eye of the subject.
 41. The system of claim 40,wherein the light pattern includes at least one circular portion. 42.The system of claim 40, wherein the control electronics is configured toanalyze the image data by at least one of: performing a Hough transformof the image data, fitting the image data and measuring a goodness offit, and performing image correlation with one or more geometric markertemplates.
 43. The system of claim 42, wherein the control electronicsis configured to analyze the image data by performing the Houghtransform of the image data.